here is a link to your Product and motherboard's specs. Anything in the socket MPGA478 Pentium 4 Willamett and Northwood line is supported according to HP's published specs. Processor FSB should be 400Mhz.
Memory: you are actually better off staying within the PC2100/1600 range for compatibility reasons. I know those old memory sticks are harder to find than PC2700 sticks are.